Define nitrogen estimation - kjeldahl''s method, Biology

Assignment Help:

Define Nitrogen Estimation - Kjeldahl's Method?

Nitrogen in the protein is estimated by a method referred to as Kjeldahl's method. Although over a period of time many other methods have emerged for determination of organic nitrogen, this method still remains an old favourite because it is reliable and has very well standardized procedures. The method involves the digestion of the weighed sample with concentrated sulphuric acid, selenium oxide, potassuim sulphate and copper sulphate in a long necked special digestion flask known as kjeldahl's flask. Potassium sulphate increases the boiling point of the mixture. Since the digestion results in fuming of the sulphuric acid, the procedure has to be carried out in a fume hood and the procedure takes several hours. The sample is digested until the solution in the digestion flask becomes clear after which it is transferred to an appropriate volumetric flask (usually 50 or 100 ml flask) and the volume is made up to the mark with distilled water. Aliquots of this sample are used for distillation in the kjeldahl's apparatus and nitrogen in the protein is estimated. Most proteins contains 16% nitrogen. Thus, percent nitrogen content is multiplied by 6.25 to get crude protein content.

1805_Nitrogen Estimation - Kjeldahl’s Method.png

The experiment involves decomposition of ammonium sulphate by a fixed volume of alkali (NaOH). Ammonium sulphate on decomposition releases ammonia which is collected in a flask of boric acid solution Tashiro's indicator. With boric acid ammonia forms a complex 'ammoium borate'. As ammonia is distilled into the boric acid, the Tashiro indicator slowly changes colour from pink to green. This is because the colour of the indicator is pH dependent - it is pink in acidic medium and green in alkaline medium. When the green coloured solution containing the boric-acid-ammonia complex is retitrated against H2SO4, the solution slowly becomes acidic again and the indicator becomes pink. This point when colour changes from green to pink is taken as the end point.


Related Discussions:- Define nitrogen estimation - kjeldahl''s method

Human ovum, A pair of ovaries are the reproductive organs in woman. They...

A pair of ovaries are the reproductive organs in woman. They are present just below the kidneys in the abdominal cavity. Each ovary has several sac like structures called ova

What are the attribute of amylase inhibitors, What are the attribute of amy...

What are the attribute of amylase inhibitors? This has been attributed to a number of reasons, Let us see how these inhibitors act. The inhibitor forms a complex with amylase,

Explain the role of bones in human biology, Explain the role of Bones in hu...

Explain the role of Bones in human biology? Bone is covered by a tough outer membrane called the periosteum. The periosteum contains systems of capillaries that supply the bone

Explain the sinus perforations, Sinus Perforations  The maxillary antru...

Sinus Perforations  The maxillary antrum can sometimes be inadvertently penetrated. Through careful pre-operative planning using radiographs, including axial scans, this compli

The principal nitrogenous excretory in humans, The principal nitrogenous ex...

The principal nitrogenous excretory compound in humans is synthesised: 1. in kidneys but eliminated mostly through liver 2. in kidneys as well as eliminated by kidneys 3.

Explain the resorbable barriers - root perforation, Explain the Resorbable ...

Explain the Resorbable Barriers - Root Perforation It is successfully control internal bleeding through cronal access It is intended to forced in the bone, not left wi

Pluricellular organisms are formed by serial mitosis, Q. From the zygote, p...

Q. From the zygote, pluricellular organisms are formed by serial mitosis. Would this formation be possible if each cell made by mitosis had an identical life in relation to its ant

Radiography, RADIOGRAPHY You  have read  in GNM courses about radiographi...

RADIOGRAPHY You  have read  in GNM courses about radiographical examination. In this text the discussion will be on the following radiographical tests.   Chest Roentgenogram

Class holothuroidea, Class Holothuroidea Body cucumber-such as; no ar...

Class Holothuroidea Body cucumber-such as; no arms; no spines; no pedicellariae; ossicles minute and embedded in muscular wall; anus present; tube feet along with suckers; am

Function of glutamate, Q. Function of Glutamate? Glutamate It is the...

Q. Function of Glutamate? Glutamate It is the principal excitatory transmitter in the brain and is found throughout the central nervous system. Receptors Glutamate rec

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd